Field of the Invention
The present invention relates to a gas compressor disposed, for example, in an air conditioner installed in a vehicle and so on.
For example, an air conditioner for controlling an air temperature inside a vehicle is disposed in a vehicle such as an automobile. Such an air conditioner includes a loop cycle of refrigeration so as to circulate a refrigerant (cooling medium). The refrigeration cycle includes an evaporator, a gas compressor, a condenser, and an expansion valve, in order. The gas compressor in the air conditioner compresses a cooling medium in the form of gas which is vaporized by the evaporator and sends it toward the condenser as a high-pressure refrigerant gas.
As such a gas compressor, a vane-rotary type gas compressor which includes an approximately ellipsoidal cylinder and a rotor rotatably supported in the cylinder is conventionally known. In such a compressor, the rotor includes a plurality of vanes projectably and retractably disposed such that respective leading ends of the vanes slidably contact with an inner circumferential surface of the cylinder (for example, refer to Patent Document 1: Japanese Patent laid-open No. 2000-257576).
The vane-rotary type gas compressor according to Patent Document 1 includes a compressor maw body comprising a rotor which can rotate integrally with a rotational axis, a cylinder configured such that a sectional contour of an inner circumferential surface surrounds an outer circumferential surface of the rotor front the outside, a plurality of vanes arranged to be projectable from the outer circumferential surface of the rotor toward the inner circumferential surface of the cylinder, and two side blocks which cover both ends of the rotor and the cylinder and support both sides of the rotational axis to be rotatable.
By decreasing a volume of a compression room which is sectioned and formed between the outer circumferential surface of the rotor and the inner circumferential surface of the cylinder by two vanes next to each other along the rotational direction of the rotor in accordance with the rotation of the rotor, the compressor main body compresses the low-pressure refrigerant gas which is conducted into the compression room and discharges the compressed high-pressure refrigerant gas toward a discharge room. The discharged high-pressure (hereinafter, referred to as a discharge pressure) refrigerant gas is discharged outside after oil which is accumulated in the refrigerant gas is separated from the gas. The separated oil is accumulated in a bottom portion of the discharge room.
The oil accumulated in the bottom portion of the discharge room (refrigerant oil, and so on) receives a pressure front the refrigerant gas having the discharge pressure discharged to the discharge room, and is supplied to the vane groove through a drain groove which is formed on the end surface of each side blocks on the rotor side through an oil path formed in two side blocks and the cylinder. Then, the oil functions as back-pressure so that the end side portion of the vane can project from the vane groove. Herein, the oil which is supplied to the vane groove from the discharge room through the oil path and the drain groove has a medium pressure which is lower than the discharge pressure of the air inside the discharge room because of the pressure drop caused by the fact that it passes through a narrow clearance formed between a shaft and the outer circumferential surface of the rotational axis.
Herein, because the back-pressure of the vane (medium pressure) is lower than that in the general performance shortly after starting the gas compressor, and the pressure inside the compression room exceeds the centrifugal force due to the back-pressure at medium pressure and the rotation of the vane, in the final stage of the compression process, there may be the case in which chattering (repetition of separation and collision between the leading end portion of the vane and the inner circumferential surface of the cylinder) is generated.
Therefore, because the bottom portion of the vane groove which communicates with the drain groove in accordance with the rotation of the rotor is separated from the drain groove in the final stage of the compression process of the refrigerant gas, that is, the bottom portion of the vane groove and drain groove enters into a non-communicating condition, the oil is confined in the bottom portion of the vane groove. Thereby, when the vane moves in a direction in which it is retracted by sliding on the inner circumferential surface of the cylinder, the volume inside the vane groove becomes smaller, so inside the vane groove becomes high-pressure which is higher than the discharge pressure, then the high-pressure which is higher than the discharge pressure can be supplied to the vane as the back-pressure. Thereby, the chattering can be prevented.
The sectional area of the communication portion between the drain groove and the bottom portion of the vane groove gradually decreases from the communicating zone of the drain groove and the bottom portion of the vane groove to the non-communicating zone of the drain groove and the bottom portion of the vane groove in the compression process of the refrigerant gas. Herein, the back-pressure rises as the communicating area of the drain groove and the bottom portion of the vane groove decreases.
The quantity of oil which is supplied from the drain groove to the bottom portion of the vane groove in a low-speed operation increases to be larger than that in a high-speed operation between such a section (section between the portion in which the drain groove and the bottom portion of the vane groove communicates to each other and the portion in which the drain groove and the bottom section of the vane groove are separated). Therefore, the predetermined quantity of oil in the bottom portion of the vane groove cannot flow toward the drain groove side before the drain groove is separated from the bottom portion of the vane groove, so the back-pressure tends to rise. Thus, the quantity of oil in the bottom section of the vane groove (back-pressure space) increases and a problem may occur such as the back-pressure excessively rising in a high-speed operation and the abraded amount increasing because the leading end portion of the vane strongly rubs the inner circumferential surface of the cylinder.